A conventional flow meter 1, referring to FIGS. 1, 2 and 3, includes a transparent holder 10 containing a housing chamber 101 with an inlet 102 and an outlet 103 located therein communicating with each other through a flow passage 104. The flow passage 104 holds an indication ball 107. The transparent holder 10 has a recess 108 on an upper side to hold a flow scale plate 15. Incorporating the indication ball 107 with the flow scale plate 15, users can instantly see fluid flowing conditions via the transparent holder 10 from outside. The conventional flow meter 1 also has a first fastening assembly 11 with a first fastening member 111 wedged in the inlet 102 and run through thereof, a second fastening assembly 12 with a second fastening member 121 wedged in the outlet 103, an anchor plate 13 which is located on a lower side of the transparent holder 10 having a first opening 131 and a second opening 132 at two ends corresponding to the inlet 102 and outlet 103 respectively, a butting member 14 with a retaining bar 144 extended from one end into the flow passage 104 to stop the indication ball 107 from flowing out and further is retained by a latch member 146 to prevent leakage, and a regulation member 16 screwed to the first fastening member 111 to regulate fluid flowing amount within a high and low range.
The flow meter 1 constructed out of the aforesaid elements has the first and second fastening members 111 and 121 wedged respectively in the inlet 102 and outlet 103 with distal ends thereof coupled to the first and second openings 131 and 132 of the anchor plate 13 to be fastened to the transparent holder 10. The anchor plate 13 also has a plurality of fastening holes for the flow meter 1 to be fastened on a machine. As the anchor plate 13 and the transparent holder 10 are coupled through screwing rather than integrally forming, the fluid (shown by broken lines in FIG. 3) injected through the inlet 102 generates hydraulic pressure exerting on the anchor plate 13 for a long time, such that the anchor plate 13 easily tends to loosening with respect to the transparent holder 10, and then damage could take place. Thus the structure of the conventional flow meter 1 is difficult to be reinforced, and the assembly of which is also troublesome.